1. Field of the Invention
The present invention relates generally to a tape locking device for tape measures, for locking the tape after unwinding the tape from a bobbin by a desired length, and more particularly, to a tape locking device for tape measures, which includes a stopper connected to the lower portion of a locking lever and provided with a coil spring fitted over the stopper and elastically biased by the coil spring to be wedged in the gap between the part of the tape unwound from a bobbin set in a housing and the part of the tape wound around the bobbin, thus automatically locking the drawn tape after drawing a desired length of the tape, in addition to smoothly retracting the tape into the housing.
2. Description of the Prior Art
Generally, a tape measure has a housing, a coiled tape connected at its first end to a spring, and wound around a bobbin set in the housing. A tab is attached to the second end of the tape, and positioned outside a slot formed on the lower end of a wall of the housing. The tab is designed to draw the tape from the housing when pulling the tab. On the other hand, the tape is retracted into the housing by an elastic restoring force of the spring when releasing the tab.
Some tape measures with a locking device have been proposed. This locking device prevents the tape from being undesirably retracted into the housing by the elastic restoring force of the spring, even when a pulling force is removed from the tab after drawing out the tape from the housing.
FIG. 1 is a perspective view showing a conventional tape measure provided with a locking device, and FIG. 2 is a sectional view of the conventional tape measure. As shown in the drawings, the conventional tape measure has a housing 1, a coiled tape 2, and a tab 4. In general, the housing 1 has a U size to be held in a single hand. The coiled tape 2 is connected, at its first end, to a spring (not shown) and wound around a bobbin 3 set in the housing 1. The tab 4 is attached to the second end of the tape 2 for allowing a user to grasp the tape 2 when drawing out the tape from the housing 1 for measuring the length of a desired object. This tab 4 is positioned outside a slot 5 formed on the lower end of a wall of the housing 1.
The tab 4 is downwardly bent to be perpendicular to the bottom of the housing 1, thus preventing the end of the tape 2 attached to the tab 4 from entering the housing 1 through the slot 5 by the restoring force of the spring. In addition, such a bent structure allows the tab 4 to serve as a fixing hook and a contact surface with respect to an end of a measured object.
A locking lever 6 is mounted to the upper portion of the wall where the slot 5 is formed, and locks the drawn tape 2 after drawing out a desired length of tape from the housing 1, while overcoming the spring force of the spring which is applied to the tape 2 to retract the tape 2 into the housing 1.
The locking lever 6 is provided on its back surface with a compression piece 7 which moves up and down along the locking lever 6. The locking operation of the locking lever 6 is as follows. When the locking lever 6 is moved downwardly, the end of the compression piece 7 compresses the portion of the tape 2 led to the slot 5 and locks the tape 2 against its retraction by the restoring force of the spring.
On the other hand, when it is required to retract the locked tape 3 into the housing 1 through the slot 5, the locking lever 6 is moved upwardly so that the compression piece 7 is separated from the locked portion of the tape 2. Then, the drawn tape 2 is retracted into the housing 1 to be rewound around the bobbin 3.
However, such a conventional tape measure has a problem that it is inconvenient to use, since a user must move the locking lever 6 downwards to lock the tape with the drawn tape being grasped, when it is required to lock the drawn tape 2 after drawing a desired length of the tape from the housing 1 by pulling the tab 4 attached to the end of the tape 2. In addition, the conventional tape measure has another problem that the tape may be damaged or scratched, since an excessively strong compressive force is applied to the tape 2 so as to overcome the elastic restoring force of the tape 2.
The conventional tape measure has still another problem that, when the locking lever 6 is restored to its original position so as to retract the drawn tape into the housing, the tape is wound around the bobbin at an excessively high speed by the elasticity of the spring connected to the tape, thus causing a user to be sometimes injured.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a tape locking device for tape measures, which has a locking lever rotatably hinged to the upper portion of the wall of a housing, and a cylinder connected, at its first end, to the lower portion of the locking lever, and connected, at its second end, to a stopper, provided with a coil spring fitted over the cylinder, whereby the stopper is elastically biased by the coil spring to be wedged in the gap between a wound part of the tape around the bobbin and a linear part of the tape led to the slot when releasing the locking lever after drawing a desired length of tape from the slot, thus automatically locking the drawn tape, in addition to smoothly winding the tape around a bobbin set in the housing when the locking lever is pushed so that the tape is retracted into the housing.
In order to accomplish the above object, the present invention provides a tape locking device for a tape measure, the tape measure including a housing, a coiled tape connected at its first end to a spring and wound around a bobbin set in the housing, and a tab attached to the second end of the tape for allowing a user to grasp the tape when drawing out the tape, and positioned outside a slot formed on the lower end of a wall of the housing; the tape locking device comprising a locking lever hinged to the upper portion of the wall of the housing in such a way to be rotated frontward and rearward around a hinged joint, and a cylinder connected to the lower portion of a connecting piece downwardly extending from the locking lever, with a coil spring fitted over the cylinder, whereby the stopper having a cone shape and made of rubber is connected to the end of the cylinder, and elastically biased by the coil spring to be wedged into the gap between a part of the tape wound around the bobbin and a unwound part of the tape led to the slot.
Preferably, the stopper has a cone shape so as to be brought into contact simultaneously with the outer circumferential surface of the tape wound around the bobbin and the unwound part of the tape led to the slot. And, the stopper is made of a material having a predetermined friction coefficient relative to a smooth tape surface, such as rubber, or synthetic resin.
Further, the stopper is always biased by the coil spring fitted over the cylinder in a direction such that the stopper is brought into contact with both the outer circumferential surface of the tape having a radius which becomes smaller as the tape is drawn out from the housing, and the unwound part of the upper surface of the tape led to the slot.
When releasing the tape after drawing a desired length of tape from the housing, the tape tends to be retracted into the housing by the spring connected to the tape. At this time, the frictional force of the stopper is applied to the tape, such that the tape is locked as it is appropriately drawn. When pushing the locking lever mounted on the upper portion of the housing, the cylinder having the stopper moves toward the front wall of the housing to remove the stopper from the gap between the wound part of the tape and the unwound part of the tape led to the slot, thus accomplishing smooth winding of the tape around the bobbin.